The present invention generally relates to fluid treating and, more particularly, to apparatus and methods which are especially adapted for providing for improved treatment of fluids. Industrial and domestic water supplies often contain undesirable constituents which require treating prior to end use. Although capable of a variety of uses, this invention finds advantageous utility in the treatment of water to remove or inhibit the growth of undesirable constituents contained therein such as, for example, dissolved chlorine and bacteria constituents.
In this regard, industrial and utility processes often require large amounts of water for cooling. Many water cooling operations utilize heat exchange for primary heat regulation, with a resulting rise in the temperature of the cooling water passing through the equipment. This rise in temperature promotes the growth of organisms already in the water which in turn can result in fouling of the equipment such as by clogging of the system or by build-up of a biological slime layer on the heat exchange surfaces which greatly reduce their effectiveness.
Chlorination is the most common means of controlling bacteria in cooling water systems as well as in drinking water systems. While the biocial properties of hypochlorous acid are effective to kill bacteria the hypochlorous acid itself may be deliterious to other equipment or treatment systems being used. In addition excess chlorine in drinking water often imparts an undesirable taste and odor to the water and the effluent water can be harmful to the environment. In this regard, the EPA has established effluent limitations for residual chlorine and it is often necessary to utilize dechlorination procedures to remove excess residual chlorine resulting from over chlorination in order to comply with EPA guidelines.
Another advantageous utility of the present invention is in reducing the concentration of undersirable metals present in the water. This is of particular value in the treatment of drinking water. Specific standards have been set for many metals such that each metal must be below a specific concentration. It is highly desirable to have available a simple treatment that will reduce the concentration of many undersirable metals so that they will be within the established standards.
Similarly for other uses, the concentration of various metals need be at low levels to prevent interference with the proposed use of the fluid. Various commercial and industrial uses can be adversely affected by the presence of metallic contaminants such as aluminum, arsenic, barium, cadmium, chromium, copper, iron, lead, mercury, selenium and zinc. The presence of these and other undesirable metals in excess amounts can interfere with the use of the fluids in various industrial applications such as heat exchange fluids, lubricants, pressurization, and other applications.
Consequently, the presence of a method for substantially reducing the concentration of undesirable metals in water, particularly drinking water, and other fluids is of the utmost importance.
In the field of fluid treating, and particularly in the field of treating water for commercial, industrial and domestic use, a number of systems have been proposed, some or all of which have certain undesirable characteristics, drawbacks or disadvantages associated therewith.
For example, ion-exchange systems are commonly used to soften water and selectively remove specific impurities from the water. The active medium of the ion-exchanger is an ion-exchange resin which is designed to remove undesirable constituents from the fluid and replace those undesirable constituents with a less undesirable constituent. For instance, a cation exchange resin employed to remove the hardness-producing elements of calcium and magnesium may be designed to simultaneously give up sodium in exchange for the calcium and magnesium contained in the water which has passed through the ion-exchanger. Regardless of the specific ion-exchange resin used, eventually the bed of resin becomes exhausted and the unit must be removed from service and be regenerated to become use useful again. In addition to chemical exhaustion ion bacterial can quickly fill an ion-exchange resin tank and plug chemical feed nozzles and other orifices. The resin is also susceptible to chemical degradation such as by excess chlorine present from a bacterial treatment process. Accordingly, the ion-exchanger unit must be carefully maintained and monitored to assure continued acceptable performance.
Another popular type of process for treating water is reverse osmosis wherein pressure in excess of the osmotic pressure of the fluid is used to force untreated water, normally at ambient temperature, through a selective membrane in a direction opposite to that normally observed is osmotic processes. The selective membrane is designed to allow the water to permeate through while rejecting the dissolved undesirable constituents. The success of this process depends in large part upon the development of suitable membranes. Membranes utilized in reverse osmosis typically experience a variety of temperature, chemical and pressure stability problems as well as speed and capacity limitations. Just as bacteria can foul heat exchangers so can it produce a fouling film on reverse osmosis membranes. If the water supply is treated with chlorine as an antibacterial agent the dissolved chlorine, although highly effective in combating bacteria, often has a deleterious effect on reverse osmosis membranes. Additionally, reverse osmotic equipment also must be carefully set up, maintained, and monitored. Accordingly, regardless of the sophistication of the technology used, if the end user fails to maintain the system and perform the necessary sampling required to ensure that the system is functioning to design specifications a breakdown in treatment can occur.
Still another popular water treatment process is the application of activated carbon, which is widely used for taste and odor control as well as removal of organic contaminants from water by adsorbtion since activated carbon is characterized by a high adsorbtivity for gases, vapors, and colloidal solids. However, similiar to the resin in ion-exchangers, the adsorbtive capacity of the carbon is eventually depleted and the carbon either must be regenerated or replaced. Therefore a system incorporating activated carbon also requires careful monitoring to determine the effectiveness of the medium. An additional disadvantage of activated carbon is that it collects microorganisms including harmful bacteria and provides a medium upon which such harmful bacteria can multiply. As a result, the activated carbon which is suppose to be purifying the water can end up contaminating the water with harmful bacteria. In an effort to overcome this disadvantage, manufacturers have attempted to provide a bacteriostatic activated carbon media by impregnating activated carbon with silver. However, such efforts have not been totally satisfactory since it is difficult to achieve effective bacteriostatic concentrations of silver and keep within the EPA established guidelines for dissolved silver content. Silver also has other disadvantages associated with its use such as the cost of the silver itself can be prohibitive to economical water treatment.
The present invention overcomes the undesirable characteristics, drawbacks and disadvantages of the prior art by providing a fluid treating apparatus and method which employ metal particulate matter: having a redox potential which relative to the redox potential of the undesirable constituents sought to be treated favors spontaneous oxidation-reduction reactions between the metal and the undesirable constituents and/or having bacteriostatic or bactericidal properties in the case where the undesirable constituent sought to be treated is a bacteria. The metal particulate matter can be of varying mesh size, preferably of from 4 to 400 mesh based on U.S. Standard screen sizes, of any desired shape and is typically arranged in a loose bed confined within a treating tank by means which prevent the escape of the particulate matter but which, at the same time, permit fluid flow therethrough. Alternatively, techniques for adhering the particles into an aggregate porous body with the surface areas freely exposed can be utilized. Suitable techniques for forming such aggregate porous bodies include sintering and processes wherein a binder is utilized which results in all, or substantially all, of the , surface area of the particles freely exposed for contacting fluids to be treated therewith. An important embodiment of the present invention is directed to an apparatus for treating water and a water treating method which employs metal particulate matter such as zinc and copper, as well as mixtures and alloys thereof, to provide removal of undesirable contaminants such as chlorine and bacteria. In this regard, an important aspect of the present invention involves a discovery that such a method will provide economical and long lasting removal of such undesirable contaminants and thereby greatly eliminate the weak link in most treatment systems i.e. maintaining and monitoring the system on a relatively frequent basis.
Another feature of the present invention involves a method of using such a bed of metal particulate matter in conjuntion with another type of fluid treating apparatus such as activated carbon, reverse osmosis, or ion-exchange processes. In this regard, an important aspect of the present invention involves the removal of undesireable elements and compounds such as chlorine and bacteria which may be detrimental to the operation and life of other treatment methods such as activated carbon, reverse osmosis and ion-exchange processes.
Another feature of the present invention involves provision of an apparatus and a method of using such a bed of metal particulate matter in conjunction with another type of fluid treating apparatus such as activated carbon, ion-exchange or reverse osmosis. In this regard, an important aspect of the present invention involves the retardation of the growth of bacteria on such a medium and/or the destruction of bacteria which may be present on such medium.
Another feature of the present invention involves adjusting the pH of the fluid and subsequently passing it through such a bed of metal particulate matter. In this regard, an important aspect of the present invention involves regulating the pH of the fluid prior to treatment to enhance the removal of contaminants having pH dependent oxidation-reduction activities.
Another feature of the present invention involves the conjoint use of dual containers having beds of such metal particulate matter arranged in series with a pH feeder interposed therebetween. Such a method of fluid treatment allows the user to take advantage of the pH of the source fluid at the inlet of the first container to treat the contaminants that are more responsive to treatment at the original source fluid pH and then to adjust the pH to treat contaminants which may be more effectively treated at another pH value to subsequently treat the fluid again in the second container.
It is therefore, an important object to the present invention to provide an improved fluid treating apparatus and method.
Another object of the invention is to provide a fluid treating apparatus and method which is economical to use, which has a relatively long life so as to avoid frequent maintenance and monitoring, and which eliminates the need to regenerate the treating medium and, accordingly, the need to dispose of concentrated contaminants inherent in other conventional treatment processes such as reverse osmosis and ion-exchange processes.
Another object of the invention is to provide a novel method of treating undesirable constituents such as chlorine and bacteria present in a fluid such as water without concentrating such constitutents in the treating medium.
Another object of the invention is to provide a fluid treating method which includes treating the fluid by passing the raw fluid containing undesirable constituents through a bed of metallic particulate matter characterized by a redox potential which relative to the redox potential of the undesirable constituents sought to be treated establishes conditions for spontaneous oxidation and reduction reactions between the metal particulate matter and the undesirable constituents when the fluid is in contact with the metal particles.
Another object of the present invention is to provide an improved method of treating fluids wherein the fluids are first passed through a bed of metallic particulate matter to treat undesirable constituents present such as chlorine which may be harmful to a conventional fluid treatment process such as a reverse osmosis process or an ion-exchange process and to then pass the fluid through such a conventional treatment process.
Another object of the present invention is to provide an apparatus for and improved method of treating fluids wherein the fluids are first passed through a conventional fluid treating process such as an activated carbon process and then the fluid is passed through a bed of metal particulate matter to treat undersirable constituents such as harmful bacteria.
Another object of the present invention is to provide an apparatus for and improved method of treating fluid wherein the fluids are passed through a bed containing both metal particulate matter as well as a conventional treating media such as activated carbon, ion-exchange resins, or reverse osmosis membranes to treat undesirable constituents.
Another object of the present invention is to provide an improved method for treating fluids so as to reduce the concentration of undersirable metals to levels which the fluids can be used in a variety of industrial applications by means of a system which does not require continued replenishment of the fluid treating system.
Another object of the present invention is to provide an improved method for treating water to reduce the concentration of undesirable metals to levels wherein the water meets standards for the concentration of such metallic contaminants set for drinking water.
These objects and other objects and advantages of the invention are accomplished by providing fluid treating apparatus which includes a bed of metal particulate matter and a method for treating fluid which includes passing fluid containing undesirable elements and compounds through such a bed of metal particulate matter. The particulate matter is preferably chosen from metals such as zinc and copper as well as mixtures and alloys thereof, having favorable redox potentials relative to the undesirable constituents such as chlorine sought to be treated so as to establish conditions for spontaneous oxidation and reduction reactions between the metal particular matter and the undesirable constituents when the fluid is in contact with the metal particles and/or having bacteriostatic or bactericidal properties in the case where an undesirable constituent sought to be treated is a bacteria.